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Test tone generator and SPL metering

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  • Test tone generator and SPL metering

    When it comes to an app or program to supply a sine wave, what do y'all use? Also, what brands of SPL meters would be good enough to be testing for phase issues (with that test tone). Would an iphone SPL meter be accurate enough? I'm talking a crossover point of 100hz ish.

  • #2
    I use this SPL meter / RTA most:

    https://itunes.apple.com/us/app/jl-a...ls/id388648626

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    • #3
      When you say test for phase issues I'm assuming that you are speaking of a polarity swap affecting the crossover region? However you can in most cases just do this by ear just as effectively.



      Yes ... the RTA in an iPhone should be fine for that. As always measuring with a RTA is only as good as your measurement. The exact location of your mic is critical to the measurement.
      Don Boomer

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      • #4
        I was just planning to send a sine wave at the crossover point, set the subs and the tops at something like 80 dBSPL and with both the subs and tops, look for an increase in output. I've been doing it by ear but I'd like to just try it with some measurement tools, just for fun.



        I was also going to experiment with placing the mic in multiple locations to see if and/or how it changes.

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        • #5
          You may not get an increase. What you want to do is look at the delta between polarity one way and then the other (one box only).



          You should experiment with moving the mic around. You could easily get a 10-20 dB difference between two spots only a couple of feet apart due to standing waves.
          Don Boomer

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          • #6
            Using pure tones leads to all kinds of issues... and bad data. A broad band signal (at least 1/3 octave wide using pink noise) will tell you a whole lot more, and while you can also get bad data this way, the odds are much better that the data will be better (unless you can't tell good data from bad). Don's comments are dead nuts on. Room contributions and relative positioning of the test mic are some serious challenges unless you know the signature of bad versus good data. That, takes lots of experience.
            -------------------------------------------------------------------------------------------------------------------------------------------------------------------
            Former product development engineer: Genz Benz, a KMC Music/FMIC/JAM Industries Company, continuing factory level product support and service for Genz Benz

            Currently product development engineer: Mesa Boogie

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            • #7
              I'm probably a light year away from understanding and using room contribution data, and SMAART systems in general. What I have been doing is playing music through the system and walking around just listening. Lately, it's been with the presonus + ipad. I'll play with the EQ, just to force myself to focus on a more specific band and then bring it flat -- with the tops and the subs and then both of them.

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              • #8
                You have to really watch trying to EQ low frequencies (in a room ... not outside). The reflections off the walls cause standing waves so that every 1/4 wavelength apart you are standing in a dead zone. So for 40 Hz that's roughly every 4 feet that frequency is basically dead. If you're standing there you'd probably boost the EQ, but it wont raise the level there, but again it will raise it a bunch 4 feet away and then 4 feet beyond that it will be dead again. The lengths are different of course for each frequency but basically if your ceiling height is less than 20 feet you're kidding yourself to do much of anything below about 200 Hz.
                Don Boomer

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                • #9
                  I was only using the EQ to give my ears something to easily bite down on. I do that a lot actually. If I think I want to boost or cut something (in the monitor or for specific channels), I'll bring it up (a lot) and then back down quickly. "Ear-balling".... that's all I can do, at this point. I generally never EQ the whole system under the crossover point.

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